TITLE: The Why of X
AUTHOR: Eugene Wallingford
DATE: June 26, 2009 4:01 PM
DESC:
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BODY:
Where did the title of my
previous entry
come from? Two more quick hits tell a story.
**Factoid of the Day**
On a walk the other night, my daughter asked why we
called variables *x*. She is reviewing
some math this summer in preparation to study algebra
this fall. All I could say was, "I don't know."
Before I had a chance to look into the reason, one
explanation fell into my lap. I was reading an article
called
The Shakespeare of Iran,
which I ran across in a tweet somewhere. And there
was an answer: the great Omar Khayyam.
*
Omar was the first Persian mathematician to call
the unknown factor of an equation (i.e., the ***x**)
**shiy** (meaning **thing** or **something**
in Arabic). This word was transliterated to Spanish
during the Middle Ages as **xay**, and, from there,
it became popular among European mathematicians to
call the unknown factor either **xay**, or more
usually by its abbreviated form, **x**, which is
the reason that unknown factors are usually represented
by an **x**.

However, I can't confirm that Khayyam was first.
Both
Wikipedia
and
another source
also report the Arabic language connection, and the
latter mentions Khayyam, but not specifically as the
source. That author also notes that "xenos" is the
Greek word for "unknown" and so could be the root.
However, I also haven't found a reference for this
use of *x* that predates Khayyam, either.
So may be.
My daughter and I ended up with as much of a history
lesson as a mathematical terminology lesson. I like
that.
**Quote of the Day**
Yesterday afternoon, the same daughter was listening
in on a conversation between me and a colleague about
doing math and science, teaching math and science,
and how poorly we do it. After we mentioned K-12
education and how students learn to think of science
and math as "hard" and "for the brains", she joined
the conversation with:
*
Don't ask teachers, 'Why?' They don't know, and they
act like it's not important.
*

I was floored.
She is right, of course. Even our elementary school
children notice this phenomenon, drawing on their own
experiences with teachers who diminish or dismiss the
very questions we want our children to ask. **Why?**
is **the** question that makes science and math what
they are.
Maybe the teacher knows the answer and doesn't want to
take the time to answer it. Maybe she knows the answer
but doesn't know how to answer it in a way that a 4th-
or 6th- or 8th-grader can understand. Maybe he really
*doesn't* know the answer -- a condition I fear
happens all too often. No matter; the damage is done
when the the teacher doesn't answer, and the child
figures the teacher doesn't know. Science and math
are so hard that the teacher doesn't get it either!
Better move on to something else. Sigh.
This problem doesn't occur only in elementary school or
high school. How often do college professors send the
same signal? And how often do college professors
not know why?
Sometimes, truth hits me in the face when I least expect
it. My daughters keep on teaching me.
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